On January 29, 1944, the Army Air Forces invited the industry to submit concept proposals for jet fighters capable of escorting its long-range heavy bombers. Since the first jet fighters were notorious fuel hogs, they promised to have insufficient range to escort the long-range B-35 and B-36 bombers then on the drawing boards. As one possible solution to this range problem, the USAAF revived the parasite fighter idea of the early 1930s, and proposed that one solution to the problem might be for the long-range bombers to carry their protective fighters right along with them.

The McDonnell Aircraft Corporation of St Louis was the only company to respond to the proposal. McDonnell proposed a small fighter aircraft to be carried partially inside a parent B-29, B-36, or B-35 heavy bomber. However, the AAF rejected this plan in January of 1945, concluding that the fighter would have to be